Persons with chronic abdominal and pelvic pain disorders comprise a large proportion of patients seeking relief from gastroenterologists, urologists and gynecologists. Two common pelvic disorders, painful bladder syndrome (PBS) and irritable bowel syndrome (IBS), are characterized by altered bladder/bowel habits (e.g., urge, frequency and, in IBS, stool consistency), pain and hypersensitivity. These patients typically exhibit significantly lower response thresholds to provocative stimuli (e.g., cystometry, rectal distension), complain of increased sensitivity during normal organ function, and exhibit increased tenderness in areas of somatic referral which, in addition, are expanded in size. Interestingly, PBS and IBS exist in the absence of an apparent pathobiological cause and are thus characterized as 'functional.'It is widely assumed that functional disorders reflect altered CNS processing, but considerable evidence suggests that persistent afferent drive contributes significantly to the recurrent, unexplained pain and hypersensitivity that characterize them. The objective of this proposal is to determine the mechanisms by which pain and hypersensitivity arise and is maintained as a necessary step in developing better informed and more successful management strategies. The Aims include: 7 Aim 1: characterize the proportions of mechano-sensitive and insensitive afferents in electrophysiological experiments in the both the lumbar splanchnic and pelvic nerve innervations of the bladder and colorectum. 7 Aim 2: evaluate organ hypersensitivity in behavioral experiments, after which the proportions of bladder and colorectal mechanically insensitive afferents (MIAs) will be determined in bladder and colorectum removed from hypersensitive mice. We hypothesize the proportions of MIAs will be significantly reduced in organs from hypersensitive mice relative to normal controls. 7 Aim 3: identify the 'chemotypes'of mechano-sensitive and insensitive bladder and colorectal dorsal root ganglion neurons in both the lumbar splanchnic and pelvic nerve pathways. We hypothesize that there are significant differences in chemotype between MIAs and mechanosensitive afferents as well as between different mechanosensitive afferents and, further, between organs. PUBLIC HEALTH RELEVANCE: Painful bladder syndrome and irritable bowel syndrome are chronic, debilitating visceral disorders, more common in women, in which pain and hypersensitivity are the most troubling symptoms. These disorders are notoriously difficult to manage. The objective of this research is to determine the mechanisms by which organ pain and hypersensitivity arises and is maintained as a necessary step in developing better informed and more successful management strategies.